2,2',2"-Nitrilo[triethyl-tris-(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2 '-diyl) phosphite] is a compound having the formula I ##STR1##
This compound of formula I is useful as a processing stabilizer for organic polymers as taught in U.S. Pat. Nos. 4,318,845 and 4,374,219. The compound of formula I is disclosed as being a white powder melting at 121.degree.-134.degree. C. As such, the powdery product has defects in terms of handling and apparent density, exhibiting poor flowability, meterability, storage stability and hydrolytic stability.
It has now been found that the compound of formula I can be obtained in a different crystalline modification as purified crystalline particles which exhibit acceptable properties in respect to handling, apparent density, flowability, meterability, storage stability and hydrolytic stability.
The new modification is characterized by a monoclinic crystalline form, melting in the range of 145.degree.-165.degree. C. as given by the peak temperature of the endotherm recorded by differential scanning calorimetry (DSC); and by an X-ray diffraction pattern obtained using Cu-K.alpha. which exhibits diffraction angles (2.THETA.) of relative intensity given in the table below.
______________________________________ Diffraction Relative Angle (2.THETA.) Intensity (%) ______________________________________ 5.2 100 5.8 38 6.3 13 6.5 15 7.2 14 8.0 30 8.7 31 8.9 36 10.0 35 10.1 31 10.7 41 11.6 18 12.7 7 13.6 20 14.2 23 14.9 18 15.7 30 16.2 31 16.6 48 17.0 28 17.4 58 18.2 37 18.7 20 19.6 20 20.0 17 20.2 17 20.8 17 21.1 18 22.6 18 22.7 18 22.9 18 23.1 16 ______________________________________
The X-ray diffraction pattern thus shows angles (2.THETA.) lines of very high intensity at 5.2; lines of high intensity at 10.7, 16.6 and 17.4; lines of medium intensity at 5.8, 8.0, 8.9, 10.0, 10.1, 10.7, 15.7, 16.2 and 18.2; lines of weak intensity at 6.3, 6.5, 7.2, 11.6, 12.7, 13.6, 14.2, 14.9, 17.0, 18.7 and 19.6; and a relative absolute configuration of the three stereo axes of the dibenzo[d,f][1,3,2]dioxaphosphepin rings of R*,R*,R*.
R* follows the customary convention when the absolute configuration of a molecule is unknown. The nomenclature adopted here is based on recent Chemical Abstracts Service practice as described by L. C. Cross and W. Kylne, Pure Appl. Chem. 45, 11-30 (1976).
The instant invention also relates to processes for the preparation of this novel alpha crystalline modification of the compound of formula I.
The instant invention also pertains to a composition stabilized against thermal, oxidative and actinic induced degradation which comprises
(a) a polyolefin, and
(b) an effective mount of the alpha crystalline form of 2,2',2"-nitrilo[triethyl-tris-(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2, 2'-diyl) phosphite], characterized by melting in the range of 145.degree.-165.degree. C. and by an X-ray diffraction pattern exhibiting lines of very high intensity at 5.2; lines of high intensity at 10.7, 16.6 and 17.4; lines of medium intensity at 5.8, 8.0, 8.9, 10.0, 10.1, 10.7, 15.7, 16.2 and 18.2; lines of weak intensity at 6.3, 6.5, 7.2, 11.6, 12.7, 13.6, 14.2, 14.9, 17.0, 18.7 and 19.6; and a relative configuration of the three dibenzo[d,f][1.3.2]dioxaphosphepin rings of R*,R*,R*.
Preferably, the polyolefin is polypropylene.
The instant alpha crystalline modification is obtained by a process of crystallizing or recrystallizing the compound of formula I from a mixture of an aromatic hydrocarbon solvent and an alcohol of 1 to 3 carbon atoms; from an ether solvent; from an ester solvent; or from a mixture of a halogenated aliphatic hydrocarbon solvent and a lower carbon chain alcohol.
The preferred process for preparing the novel alpha crystalline modification is by crystallizing or recrystallizing the compound of formula I from a mixture of an aromatic hydrocarbon solvent and a lower carbon chain alcohol.
A preferred embodiment of the instant process involves isolating the crystalline mass from any of the above processes and drying it under vacuum at elevated temperature.
Examples of aromatic hydrocarbon solvents useful in the instant process are benzene, toluene, o-xylene, m-xylene, p-xylene, 1,2,3-trimethylbenzene, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, 1,2,4,5-tetramethylbenzene, ethylbenzene, cumene, o-cymene, m-cymene, p-cymene, o-diisopropylbenzene, m-diisopropylbenzene, p-diisopropylbenzene, and mixtures of such aromatic hydrocarbon solvents.
Examples of lower carbon chain alcohols of 1 to 3 carbon atoms are methanol, ethanol, 1-propanol, isopropanol and mixtures of such lower alkanols.
Examples of ester solvents are methyl formate, ethyl formate, methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, amyl acetate and the like.
Examples of ether solvents are diethyl ether, diisopropyl ether, methyl tert-butyl ether and the like.
Examples of halogenated aliphatic hydrocarbon solvents are methylene chloride, chloroform, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane and the like.
Differential scanning calorimetry (DSC) measurements are obtained on a TA Instrument Inc., 910 differential scanning calorimeter, with a 100 mL/min nitrogen purge, aligned aluminum pan, temperature scan at 5.degree. C./min to 230.degree. C.
X-ray diffraction patterns are recorded on a Philips Norelco X-ray Diffractometer unit, using Cu-K.alpha. radiation with a nickel filter.